Add RM_TryAlloc (#10541)

Similarly to LCS, some modules would want to try to allocate memory, and
fail gracefully if the allocation fails

src/module.c

@@ -464,11 +464,18 @@ static int moduleConvertArgFlags(int flags);
 /* Use like malloc(). Memory allocated with this function is reported in
  * Redis INFO memory, used for keys eviction according to maxmemory settings
  * and in general is taken into account as memory allocated by Redis.
- * You should avoid using malloc(). */
+ * You should avoid using malloc().
+ * This function panics if unable to allocate enough memory. */
 void *RM_Alloc(size_t bytes) {
     return zmalloc(bytes);
 }
 
+/* Similar to RM_Alloc, but returns NULL in case of allocation failure, instead
+ * of panicking. */
+void *RM_TryAlloc(size_t bytes) {
+    return ztrymalloc(bytes);
+}
+
 /* Use like calloc(). Memory allocated with this function is reported in
  * Redis INFO memory, used for keys eviction according to maxmemory settings
  * and in general is taken into account as memory allocated by Redis.
@@ -12241,6 +12248,7 @@ void moduleRegisterCoreAPI(void) {
     server.moduleapi = dictCreate(&moduleAPIDictType);
     server.sharedapi = dictCreate(&moduleAPIDictType);
     REGISTER_API(Alloc);
+    REGISTER_API(TryAlloc);
     REGISTER_API(Calloc);
     REGISTER_API(Realloc);
     REGISTER_API(Free);

src/redismodule.h

@@ -861,6 +861,7 @@ typedef struct RedisModuleTypeMethods {
 #endif
 
 REDISMODULE_API void * (*RedisModule_Alloc)(size_t bytes) REDISMODULE_ATTR;
+REDISMODULE_API void * (*RedisModule_TryAlloc)(size_t bytes) REDISMODULE_ATTR;
 REDISMODULE_API void * (*RedisModule_Realloc)(void *ptr, size_t bytes) REDISMODULE_ATTR;
 REDISMODULE_API void (*RedisModule_Free)(void *ptr) REDISMODULE_ATTR;
 REDISMODULE_API void * (*RedisModule_Calloc)(size_t nmemb, size_t size) REDISMODULE_ATTR;
@@ -1191,6 +1192,7 @@ static int RedisModule_Init(RedisModuleCtx *ctx, const char *name, int ver, int
     void *getapifuncptr = ((void**)ctx)[0];
     RedisModule_GetApi = (int (*)(const char *, void *)) (unsigned long)getapifuncptr;
     REDISMODULE_GET_API(Alloc);
+    REDISMODULE_GET_API(TryAlloc);
     REDISMODULE_GET_API(Calloc);
     REDISMODULE_GET_API(Free);
     REDISMODULE_GET_API(Realloc);